Semaphorins are endogenous proteins which are identified as a factor that can retract the nerve growth cone and suppress the axonal growth. Until now, about 20 kinds of molecular species thereof have been known. Amongst them, class type 3 subfamily gene cluster has been studied the most. The proteins that these genes encode are known to have in vitro potent activities for inhibiting neurite outgrowth and retracting growth cone. Amongst them, semaphorin 3A (Sema3A) (Non-Patent Literatures 1 and 2) has been studied the most, which can induce the growth cone retraction in cultural neuron, in a low concentration of 10 pM and in a short time.
Some substances inhibiting the Sema3A function have been already known, such as a certain group of xanthone compounds which are obtained from the culture of Penicillium sp. SPF-3059 strain (International Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology, Accession number: FERM BP-7663) (Patent Literatures 1 and 2), and xanthone derivatives which are obtained by chemically-modifying the above xanthane compounds (Patent Literature 3).
And, it has been reported that the compounds can promote re-elongating the nerve fiber in spinal cord of a rat spinal cord injury model (Patent Literature 4 and Non-Patent Literature 3) and can promote regenerating the corneal sensory neuron of a mouse corneal graft model (Patent Literature 5 and Non-Patent Literature 4).